Chemoselective Activation of sp³ vs sp² C–H Bonds with Pd(II)

The first selective coupling of a carbon nucleophile with methyl, ethyl, propyl, and butyl arenes in the absence of a directing group is described. Pd­(OAc)2 double C–H activation displays remarkable selectivity for the terminal methyl sites in alkyl arenes, rather than the more commonly observed arene sp2 C–H activation. Mechanistic studies indicate the intermediacy of an azlactone dimer, obtained from oxidation with Pd­(OAc)2, and are consistent with a Pd-catalyzed C–H activation vs a radical process. The observed reactivity establishes that typical reaction solvents (e.g., toluene) can readily participate in C–H activation chemistry.